Synthesis of Highly Enantioenriched Sulfonimidoyl Fluorides and Sulfonimidamides by Stereospecific SuFEx Reaction

Sulfonimidamides present exciting opportunities as chiral isosteres of sulfonamides, with potential for additional directional interactions. Here we present the first modular enantioselective synthesis of sulfonimidamides, including the first stereoselective synthesis of enantioenriched sulfonimidoyl fluorides, and studies on their reactivity. A new route to sulfonimidoyl fluorides is presented from solid bench-stable, NBoc-sulfinamide salt building blocks. Enantioenriched arylsulfonimidoyl fluorides are shown to be readily racemized by fluoride ions. Conditions are developed which trap fluoride, and enable the stereospecific reaction of sulfonimidoyl fluorides with primary and secondary amines (100% es) generating sulfonimidamides with up to 99% ee. Aryl and alkyl sulfonimidoyl fluoride reagents are suitable for mild late stage functionalization reactions, exemplified by coupling with a selection of complex amines in marketed drugs.

Synthesis of Highly Enantioenriched Sulfonimidoyl Fluorides and Sulfonimidamides by Stereospecific SuFEx Reaction

Sulfonimidamides present exciting opportunities as chiral isosteres of sulfonamides, with potential for additional directional interactions. Here we present the first modular enantioselective synthesis of sulfonimidamides, including the first stereoselective synthesis of enantioenriched sulfonimidoyl fluorides, and studies on their reactivity. A new route to sulfonimidoyl fluorides is presented from solid bench-stable, NBoc-sulfinamide salt building blocks. Enantioenriched arylsulfonimidoyl fluorides are shown to be readily racemized by fluoride ions. Conditions are developed which trap fluoride, and enable the stereospecific reaction of sulfonimidoyl fluorides with primary and secondary amines (100% es) generating sulfonimidamides with up to 99% ee. Aryl and alkyl sulfonimidoyl fluoride reagents are suitable for mild late stage functionalization reactions, exemplified by coupling with a selection of complex amines in marketed drugs.

Bacterial Catabolism of β-Hydroxypropiovanillone and β-Hydroxypropiosyringone Produced in the Reductive Cleavage of Arylglycerol-β-Aryl Ether in Lignin

ABSTRACTSphingobiumsp. strain SYK-6 converts four stereoisomers of arylglycerol-β-guaiacyl ether into achiral β-hydroxypropiovanillone (HPV) via three stereospecific reaction steps. Here, we determined the HPV catabolic pathway and characterized the HPV catabolic genes involved in the first two steps of the pathway. In SYK-6 cells, HPV was oxidized to vanilloyl acetic acid (VAA) via vanilloyl acetaldehyde (VAL). The resulting VAA was further converted into vanillate through the activation of VAA by coenzyme A. A syringyl-type HPV analog, β-hydroxypropiosyringone (HPS), was also catabolized via the same pathway. SLG_12830 (hpvZ), which belongs to the glucose-methanol-choline oxidoreductase family, was isolated as the HPV-converting enzyme gene. AnhpvZmutant completely lost the ability to convert HPV and HPS, indicating thathpvZis essential for the conversion of both the substrates. HpvZ produced inEscherichia colioxidized both HPV and HPS and other 3-phenyl-1-propanol derivatives. HpvZ localized to both the cytoplasm and membrane of SYK-6 and used ubiquinone derivatives as electron acceptors. Thirteen gene products of the 23 aldehyde dehydrogenase (ALDH) genes in SYK-6 were able to oxidize VAL into VAA. Mutant analyses suggested that multiple ALDH genes, including SLG_20400, contribute to the conversion of VAL. We examined whether the genes encoding feruloyl-CoA synthetase (ferA) and feruloyl-CoA hydratase/lyase (ferBandferB2) are involved in the conversion of VAA. Only FerA exhibited activity toward VAA; however, disruption offerAdid not affect VAA conversion. These results indicate that another enzyme system is involved in VAA conversion.IMPORTANCECleavage of the β-aryl ether linkage is the most essential process in lignin biodegradation. Although the bacterial β-aryl ether cleavage pathway and catabolic genes have been well documented, there have been no reports regarding the catabolism of HPV or HPS, the products of cleavage of β-aryl ether compounds. HPV and HPS have also been found to be obtained from lignin by chemoselective catalytic oxidation by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone/tert-butyl nitrite/O2, followed by cleavage of the β-aryl ether with zinc. Therefore, value-added chemicals are expected to be produced from these compounds. In this study, we determined the SYK-6 catabolic pathways for HPV and HPS and identified the catabolic genes involved in the first two steps of the pathways. Since SYK-6 catabolizes HPV through 2-pyrone-4,6-dicarboxylate, which is a building block for functional polymers, characterization of HPV catabolism is important not only for understanding the bacterial lignin catabolic system but also for lignin utilization.

Highly enantioselective metallation–substitution alpha to a chiral nitrile

Nitrile anions do not necessarily lack stereochemical integrity and we show good results for stereospecific reaction with a simple magnesium base.